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  2. ICD-10-CM Codes List
  3. G00–G99
  4. G30-G32
  5. Other degenerative diseases of nervous system, not elsewhere classified (G31)

Other degenerative diseases of nervous system, not elsewhere classified (G31)

The ICD-10 code section G31 covers a variety of other degenerative diseases of the nervous system not classified elsewhere. These codes are used for diagnosing less common or specific neurological disorders that involve progressive nerve damage and loss of brain function.

This section includes important conditions such as G31.0 frontotemporal dementia, and its specific forms like G31.01 Pick's disease, which is known for symptoms including behavioral changes and language difficulties. Pick's disease is also referred to by synonyms like "Progressive aphasia" or "Dementia due to Pick's disease," helping coders identify it precisely. G31.09 captures other frontotemporal neurocognitive disorders, including familial and genetic variants. The codes also cover degeneration due to alcohol (G31.2), neurocognitive disorder with Lewy bodies (G31.83), and mild cognitive impairment of unclear cause (G31.84). Rare hereditary disorders such as Leigh’s disease (G31.82) and Alexander disease (G31.86) are included as well. For unspecified or mixed presentations, G31.8 and G31.9 offer coding options. Using the appropriate ICD-10 code for degenerative nervous system disease ensures accurate diagnosis and treatment planning for these complex neurological conditions.

Instructional Notations

Use Additional Code

The “use additional code” indicates that a secondary code could be used to further specify the patient’s condition. This note is not mandatory and is only used if enough information is available to assign an additional code.

Type 2 Excludes

A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

Clinical Terms

The following clinical terms provide additional context, helping users better understand the clinical background and common associations for each diagnosis listed in this section. Including related terms alongside ICD-10-CM codes supports coders, billers, and healthcare professionals in improving accuracy, enhancing documentation, and facilitating research or patient education.

Alexander Disease

Rare leukoencephalopathy with infantile-onset accumulation of Rosenthal fibers in the subpial, periventricular, and subependymal zones of the brain. Rosenthal fibers are GLIAL FIBRILLARY ACIDIC PROTEIN aggregates found in ASTROCYTES. Juvenile- and adult-onset types show progressive atrophy of the lower brainstem instead. De novo mutations in the GFAP gene are associated with the disease with propensity for paternal inheritance.

Corticobasal Degeneration

Rare progressive neurological disorder characterized by Parkinsonism, cortical atrophy of multiple areas of the brain including the cerebral cortex and the basal ganglia, cognitive dysfunction and eye movement abnormalities.

Frontotemporal Dementia

The most common clinical form of FRONTOTEMPORAL LOBAR DEGENERATION, this dementia presents with personality and behavioral changes often associated with disinhibition, apathy, and lack of insight.

Frontotemporal Lobar Degeneration

Heterogeneous group of neurodegenerative disorders characterized by frontal and temporal lobe atrophy associated with neuronal loss, gliosis, and dementia. Patients exhibit progressive changes in social, behavioral, and/or language function. Multiple subtypes or forms are recognized based on presence or absence of TAU PROTEIN inclusions. FTLD includes three clinical syndromes: FRONTOTEMPORAL DEMENTIA, semantic dementia, and PRIMARY PROGRESSIVE NONFLUENT APHASIA.